The long-term goal of this work is to elucidate the biophysical and biochemical mechanisms underlying visual excitation and adaptation. A deep understanding of the visual system itself is, of course, highly desirable in order to understand how it might be affected in abnormal states brought on by disease and genetic defects. In addition, the visual system is probably the most accessible of a very large family of signal transduction systems that are found in all vertebrates and invertebrates; these signal transduction systems are all based on cell surface receptors that are coupled to GTP binding proteins (G proteins). Visual pigments are examples of such G protein-coupled cell surface receptors. The findings will, therefore, have important ramifications to the understanding of odorant, hormone and neurotransmitter signaling. The approach is to use both the broad range of naturally-occurring visual systems, not only the rhodopsin/rod system, but long wavelength cone systems, mixed rod/cone systems like gecko, very short wavelength cone systems like human blue cone, and invertebrate systems such as octopus. The investigators seek to understand the similarities and differences between vision based on these distinct categories of pigments. They will focus on the events leading up to the formation of the active state of a visual pigment. They will utilize low temperature, flash-induced kinetics, FTIR (Fourier transform infrared) spectroscopies as well as light-induced photocurrents to study the transformations that a visual pigment undergoes leading up to its active state.